Specimen heating device

ABSTRACT

A device for holding and heating a specimen for an X-ray apparatus, for example, an X-ray diffractometer. The device comprises a heater ribbon of an electrical resistance heating material having a flat specimen face. There is a recess cut in the heater ribbon for housing the specimen such that substantial sample temperature uniformity is achieved.

tates atent I'mo [ Apr-.10, 1973 SPECIMEN HEATING DEVICE [75] Inventor:Masaaki Hino,

Akishima-shi, Japan [73 Assignee1, Nihon Denshi Kabushiki Kaisha, Tokyo,Japan Showa-machi,

[22] Filed: Mar. 10, 1971 [21] Appl. No.1 122,811

52 us. Cl ..250/51.5 [511 Int. Cl. ..GOln 23/20 [58] Field of Search..250/51.5

[56] References Cited V UNITED STATES PATENTS 3,148,275 9/1964 Mack..250/515 3,113,209 12/1963 Shimula ...250/51.5

OTHER PUBLICATIONS I Study of Phase Transitions High-Temperature X-RayDiffractometer by J. A.

in W0 with a Perr, et al., from the Journal of Applied Physics, Vol. 28,No. 11, Nov. 1957, pages 1272-1275. Adaptation of a Geiger-Counter X-RayDiffractometer for High-Temperature Investigations by P. Chiotti fromThe Review of Scientific Instruments, Vol 25, N0. 7, July 1954, pages683-688.

High Temperature, High Vacuum, Diffractometer Attachment, by J. lntrateret al. from The Review of Scientific Instruments, V01. 32, No. 8, Aug.1961,

pages 905 & 906.

Primary ExaminerWilliam F. Lindquist Attorney-Webb, Burden, Robinson &Webb ABSTRACT A device for holding and heating a specimen for an X- rayapparatus, for example, an X-ray diffractometer. The device comprises aheater ribbon of an electrical resistance heating material having a flatspecimen face. There is arecess cut in the heater ribbon for housing thespecimen such that substantial sample temperature uniformity isachieved.

3 Claims, 8 Drawing Figures PAIENTEDAPR 1 01915 3,727, 052

sum 1 UF 3 k W mm PATENTEU 1 0 3, 727, 052

SHEET 2 [IF 3 PATENTEDAPR 1 0 1915 sum 3 0F 3 qv @Pi SPECIMEN HEATINGDEVICE The present invention relates to a specimen heating device foruse in an X-ray apparatus, especially an X- ray diffractometer. Y

Specimen heating devices of one type or another are frequently used inX-ray diffractometers to enable the analysis of the structure ofcrystals at elevated temperatures. For example, in the specimen heatingdevice described in US. Pat. No. 3,051,835, the specimen is adjacent tobut does not directly touch the heating device and the temperature ofthe specimen is raised by heat radiation or convection of heat from theheating means. In such a device heat is easily dissipated before beingtransferred to the specimen. Moreover, the resulting low thermalefficiency makes necessary numerous windings on the heater to maintainthe specimen at the required temperature and provides adequatetemperature uniformity. This results in high consumption of power.

A device has been proposed in which the specimen is directly mounted onthe heater ribbon. Unfortunately, the advantages of such a deviceoutweigh the disadvantages. For example, the specimen is not securelyfixed to the heater ribbon and frequently slips off the ribbon surfacewhen tilted during analysis. Further, if the specimen happens to befairly electrically conductive, it becomes difficult to heat thespecimen to a sufficiently high temperature. Still further, the heateris liable to break, since the part of the heater on which the specimenis mounted remains cooler than the surrounding area. Also, thetemperature of the specimen is not uniform over the entire area. Theedges are somewhat cooler than the center part due to greater thermalradiation at the edges than at the center.

Briefly, according to this invention, a device for heating an X-rayspecimen comprises a heater ribbon of an electrical resistance heatingmaterial. Exemplary heating materials are platinum rhodium alloys. Theends of the heater ribbon are suitably attached to an adjustable currentsupply. The ribbon has a flat specimen face with a recess cut into thespecimen face for housing the specimen. Preferably, the ratio of thedepth of the recess (at its central point) to the thickness of theheater ribbon is between 0.3 and 0.6. It is also preferred that theratio of the width of the recess to the width of the heater ribbon isbetween 0.7 and 1. It is clear, of course, that the ratio cannot beprecisely 1 or the width of the recess would extend entirely across theribbon.

It is an advantage of the present invention to provide an improvedspecimen heating device enabling the specimen to be easily positioned onthe heater ribbon. It is an additional advantage of the presentinvention to provide an improved specimen heating device enabling thespecimen to be heated to a high temperature with high efficiency. It isa further advantage of the present invention to provide an improvedspecimen heating device which maintains substantially uniform specimentemperature of the entire sample.

The invention will be more fully understood by reading the followingdetailed description in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic diagram of an X-ray diffractometer incorporating aspecimen heating device according to this invention;

FIG. 2 is a perspective view of a heating ribbon according to'thisinvention;

FIG. 3 is a sectional view of the embodiment shown in FIG. 2;

FIGS. 4 A-C show the temperature distribution of the specimen accordingto the type or design of heater ribbon used; and,

FIGS. 5 and 6 are sectional views of other embodiments of thisinvention.

Referring to FIG. 1, a radiant energy source, for example, an X-ray tubeis disposed on a focusing circle 2. An air-tight casing 3 is centrallymounted on a goniometer 41. Windows 5a and 5b are provided in the casing3 to allow the X rays produced by the X-ray tube 1 to pass throughv Aheating device 6 according to the present invention is also mounted onthe goniometer 4. A specimen 7 is placed on the said heating device andheated to the desired temperature directly. The X- radiation from theX-ray tube 1 passes through the window 5a and irradiates the specimen 7.The X-radiation X diffracted by the specimen 7 passes through the window5b and is detected by adetector 8 which is movably disposed on thefocusing circle 2. The output signal from the detector is fed into arecorder (not shown) synchronized with the goniometer 4.

When the incident angle 0 of the irradiating X ray is varied by rotatingthe goniometer 4, the detector 8 is moved along the focusing circle 2 soas to satisfy the Bragg condition. As a result, the X-ray diffractionprofile of the heated specimen is recorded on the recorder.

Referring to FIGS. 2 and 3, the specimen heating device 6 comprises aheater ribbon 9 made of, for example, platinum rhodium alloy.- The bentportions 10a and 10b of said heater ribbon 9 serve to prevent metaldeformation due to heat'expansion. A recess 13 cut into the heaterribbon houses the specimen. The recess is cut to satisfy the followingconditions enabling uniform temperatures over the entire specimensurface, viz,

0.3 g b/a 0.6 and 0.7 g d/c l where a is the thickness of the heaterribbon, b is the depth of the recess, 6 is the width of the heaterribbon and d is the width of the recess. Electrical terminals 11a and11b join the ribbon with an adjustable current supply 12.

FIG. 4a shows the temperature distribution over the specimen inaccordance with the ribbon used in the prior art having a flat surface.In this case, as apparent from the drawing, the temperaturedistributions take the form of bell-shaped curves indicating that thetemperature distribution over the specimen surface is not uniform.

FIG. 4b shows the temperature distributions when a shallow recess is cutinto the heater ribbon 9. In this case, a is 0.4 mm, b is 0.05 mm, c is14 mm and d is 12 mm. (Accordingly, b/a equals 0.125 and d/c equals0.857.) A slight improvement in the temperature distribution will beobserved but the temperature difference between the edges and centerpart of the heater is still pronounced.

By increasing the depth of the recess to 0.15 mm as shown in FIG. 4c sothat b/a 0.375, optimum temperature distribution uniformity is obtained.An increase in depth beyond 0.15 mm would further improve the uniformitybut such considerations are limited by such factors as temperatureinequality due to machining errors, possibility of heater ribbonbreakage, and the tendency of the center portion of the specimen toincrease in temperature as compared with the edges. Accordingly, in thisinvention, b/a should be maintained below 0.6. At the same time, thelower limit of d/c must not exceed 0.7. If it does, the temperaturealong the edges of the heater ribbon will not increase sufficiently dueto the large heat capacity along said edges.

FIG. 5 is a sectional view showing another embodiment of this invention.In this case, the curved bottom of the recess 13 is convex so that thedepth at the edges is greater than that in the center portion. By sodoing, the temperature along the edges is higher than that obtained inFIG. 40. FIG. 6 shows a modified version of FIG. 5, in which thepolygonal bottom of the recess has flat surfaces which form a convexsurface.

Having thus described the invention with the detail and particularity asrequired by the Patent Laws, what is desired protected by Letters Patentis set forth in the following claims.

Iclaim:

l. A holding and heating device for a specimen in an X-Ray apparatuscomprising a heater ribbon of an electrical resistance heating materialarranged to be heated by passing an electrical current therethrough,said device having at least one substantially flat specimen face, therebeing a recess in said face, said recess having sidewalls and endwallsextending downward from said flat face to a bottom face, all edges ofsaid bottom face contacting said sidewalls or endwalls, said sidewalls,endwalls and bottom face arranged for direct heat transferring contactwith said specimen.

2. A device according to claim 1 wherein the ratio of the depth of therecess to the thickness of the heater ribbon is between about 0.3 and0.6 and the ratio of the width of the recess to the width of the heaterribbon is between about 0.7 and l.

3. A device according to claim 2 wherein the bottom of the recess has aconvex configuration such that the depth of the center of the recess isless than that along the edges.

1. A holding and heating device for a specimen in an X-Ray apparatuscomprising a heater ribbon of an electrical resistance heating materialarranged to be heated by passing an electrical current therethrough,said device having at least one substantially flat specimen face, therebeing a recess in said face, said recess having sidewalls and endwallsextending downward from said flat face to a bottom face, all edges ofsaid bottom face contacting said sidewalls or endwalls, said sidewalls,endwalls and bottom face arranged for direct heat transferring contactwith said specimen.
 2. A device according to claim 1 wherein the ratioof the depth of the recess to the thickness of the heater ribbon isbetween about 0.3 and 0.6 and the ratio of the width of the recess tothe width of the heater ribbon is between about 0.7 and
 1. 3. A deviceaccording to claim 2 wherein the bottom of the recess has a convexconfiguration such that the depth of the center of the recess is lessthan that along the edges.